Investigating the Feasibility of Multi-Scan Terrestrial Laser Scanning to Characterize Tree Communities in Southern Boreal Forests

Tuomas Yrttimaa,Mikko Vastaranta,Ville Kankare,Ninni Saarinen,Markus Holopainen,Xinlian Liang,Juha Hyyppä

doi:10.3390/rs11121423

Abstract

Terrestrial laser scanning (TLS) has proven to accurately represent individual trees, while the use of TLS for plot-level forest characterization has been studied less. We used 91 sample plots to assess the feasibility of TLS in estimating plot-level forest inventory attributes, namely the stem number (N), basal area (G), and volume (V) as well as the basal area weighed mean diameter (Dg) and height (Hg). The effect of the sample plot size was investigated by using different-sized sample plots with a fixed scan set-up to also observe possible differences in the quality of point clouds. The Gini coefficient was used to measure the variation in tree size distribution at the plot-level to investigate the relationship between stand heterogeneity and the performance of the TLS-based method. Higher performances in tree detection and forest attribute estimation were recorded for sample plots with a low degree of tree size variation. The TLS-based approach captured 95% of the variation in Hg and V, 85% of the variation in Dg and G, and 67% of the variation in N. By increasing the sample plot size, the tree detection rate was decreased, and the accuracy of the estimates, especially G and N, decreased. This study emphasizes the feasibility of TLS-based approaches in plot-level forest inventories in varying southern boreal forest conditions.

Highlights

Most of the carbon in terrestrial biosphere is stored in forest ecosystems, which are key components in the global carbon cycle and biodiversity maintenance [1,2]
This study emphasizes the feasibility of Terrestrial laser scanning (TLS)-based approaches in characterizing tree communities by demonstrating a high accuracy in the estimates for plot-level forest inventory attributes for sample plots in varying southern boreal forest conditions
Stand structural complexity correlated negatively with the tree detection rate, which was the most crucial factor affecting the overall performance of the TLS-based forest inventory method

Summary

Introduction

Most of the carbon in terrestrial biosphere is stored in forest ecosystems, which are key components in the global carbon cycle and biodiversity maintenance [1,2]. Assessing carbon stores and fluxes in a forest ecosystem requires an understanding of the ecosystem functioning as ecosystem services are end products of various biochemical processes that result when individual plant communities interact with climate and each other. This means that the functionality of plant communities and the functional traits of individual plant species affect ecosystem properties [3,4]. Trees are among the most important plants, having a great impact on a forest ecosystem’s functionality and the provision of ecosystem services [5,6]. Characterizing the functionality of tree communities by means of forest inventory techniques contributes to an understanding of forest ecosystem functioning

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